Sand control in wells



Aug. 22, 1967 J. L. RIKE d 3,336,980

SAND CONTROL 1N WELLS Original Filed Nov. 25, 1964 FIG.2. Y/

A LLowING APLAsTI O INVENTOR.

JAMES L. RIKE,

g3* BY ATTORNEY.

//l/ ff WELL FLOw f A/ I REMOVING soLIOsQ/ 3,336,980 SAND CONTROL IN WELLS James L. Rike, New Orleans, La., assignor, by mesne assignments, to Esso Production Research Company, Houston, Tex., a corporation of Delaware Continuation of abandoned application Ser. No. 413,941, Nov. 25, 1964. This application Feb. 9, 1967, Ser. No.

11 Claims. (Cl. 166-33) ABSTRACT F THE DISCLOSURE This application is a continuationof application Ser. No. 413,941, entitled, Sand Control in Wells, filed Nov. 25', 1964, now abandoned, by James L. Rike.

This invention relates generally to the control of sand production from oil and gas wells through which earth fluids are produced from unconsolidated subsurface formations.

When fluids are produced from loosely consolidated, subsurface formations, sand is also produced. One technique for controlling sand production when producing uids from unconsolidated formations involves the treatment of the unconsolidated sand with thermosetting plastics or resins. When the plastic sets, it binds the sand particles together, but permits Well liuids to flow to the well bore.

Both phenol-formaldehyde and epoxy-type resins have been successfully used to consolidate sands in the field. U.S. Patent No. 3,022,825, issued Feb. 27, 1962, to W. O. Winsauer et al., entitled, Method for Sand Consolidation; U.S. Patent No. 3,047,067, issued July 3l, 1962, to R. E. Williams et al., entitled, Sand Consolidation Method; and U.S. Patent No. 3,097,692, issued July 16, 1963, to Williams et al., entitled, Sand Consolidation Method, illustrate a few of the practical sand consolidation methods using resins that have been employed in the past.

Although the process of sand consolidation with plastics or resins has been successful in many wells with a wide range of depth and with widely varying well conditions, it has not always been successful. Repeated treatments have been necessary in some wells to successfully control the sand production. In other wells sand production was controlled but productivity of the wells was much lower than anticipated. In some fields, resinconsolidated wells produced less than 80 bbls./day with tubing pressures of 20 to 100 p.s.i., whereas other wells completed in the same or similar formations demonstrated a capability of over 100 bbls./day at tubing pressures 400 p.s.i. and above.

The present invention provides a method which overcomes the defects in sand control and lack of well productivity when resins are used to consolidate incompetent sands. A limited void space is allowed to form or is intentionally created on the formation side of the perforation hole; and this void is maintained with fluid movement during the sand consolidating process and the void and perforation hole are packed immediately thereafter with a solid material, which is later flowed back from United States Patent O 3,336,980 Patented Aug. 22, 1967 ice the perforation hole upon resumption of production, after the consolidating resins have set around the sand grains beyond the void space.

A primary object, then, of the present invention is to provide a method for improving the success ratio of consolidating incompetent sands in subsurface formations through use of resin-strengthening techniques. Another primary object is the improvement of well productivity in resin-consolidated Wells.

Other objects and advantages of the invention will become apparent from the following, more detailed description of the invention when taken with the accompanying drawing wherein:

FIG. 1 is a cross-sectional view of a borehole penetrating a subsurface formation illustrating the perforating step of the invention; and

FIGS. 2 through 6 are schematic cross-sectional diagrams of a portion of the Well bore and surrounding earth formations illustrating the sequence of steps applied in accordance with the teachings of the invention.

The present practice in the art of consolidating the sands of incompetent formations with plastics includes the following steps:

(l) The casing is cemented in the well bore.

(2) A perforator gun is lowered to adjacent the incompetent productive formation and the formation is perforated with care `taken to insure that no sand will be produced from the formation during the perforating operation.

(3) The perforator gun is withdrawn and a small, concentric pipe is run in the casing and plastic materials are pumped through the small pipe and displaced into the formation through the pcrforations. During placement of the plastic, care is taken to prevent even momentary flow of fluids into the Well bore.

(4) The plastic materials are allowed to harden or set.

Fluid of sufficient Weight to con-trol the well is circulated through the small pipe and then the small pipe is withdrawn from the well bore.

(5) The well is placed on production, usually by swabbing.

In this operation, in accordance with current practice, all of the gun debris resulting from the perforating process tends to enter the perforation hole and become packed and consolidated in it as a result of the differential iluid pressure and the flow of resin into the hole. Even if the gun debris falls out of the perforation hole or is not of sufficient volume to restrict flow, the loose formation sands would tend to fill a portion of the perforation hole during the time it takes the plastic to set. This flow of sand into a portion of the perforation hole would occur despite pressure equilibrium because the formation sand has a higher specific gravity than the Well fluids. Gravity would tend to cause the hole to fill with the loose sand located immediately above the perforation holes. This loose sand accumulating in the perforation holes during the period prior to placing the plastic in the formation would become wet with plastic and would harden into strong consolidated sand particles when the curing or setting time for the resin had elapsed. The high pressure differential requiredl in moving resin liquids into the formation suggests that the reasons for poor consolidation in some areas are attributable to packing the perforation holes with gun debris in the aforementioned manner. Darcys law indicates that a ow of 25 bbls. of 3 cp. fluid daily through a 1/2 diameter by 2 long cylinder of 300 md. sand would require a pressure differential in eX- cess -of 20,000 p.s.i. It is seen, then, how the present Consolidation practice might easily result in reduced or zero productivity if only a fraction of the perforation hole is filled with consolidated sand. The reduced productivity sometimes results in sand control failure because of the high differential pressures incurred in trying to stimulate flow.

If gun debris which has little or no permeability is left packed in the perforation hole, the consolidation plastic may be directed down a channel formed between the cement and the formation before the plastic enters the unconsolidated sand formation. The frequent use of fracturing pressures in consolidation treatments is a strong indication of this occcurrence. If sand adjacent to and immediately beyond the perforation hole is left unconsolidated, then an apparent failure in sand control would result even though consolidating plastic had consolidated the sand at some lower or higher point through a fracturing technique.

Operation With reference to the figures for a more complete description of the operation of the present invention, in FIG. l a casing is shown surrounded by cement 11 and penetrating a unconsolidated formation 12. A perforator gun 13 is positioned adjacent formation 12 and perforations 14 are formed in formation 12 when gun 13 is fired. According to the method of the invention, perforator gun 13 is lowered through casing 10 to adjacent unconsolidated formation 12 where it is fired with a differential pressure preferably into the well bore, P1 P2 to create perforation holes 14. Approximately one barrel of iiow from the unconsolidated formation 12 through perforations 14 is then permitted. If necessary, the one barrel of iiow is induced by swabbing. Gun 13 is then withdrawn from the well bore.

FIG. 2 illustrates the unconsolidated formation after it has been perforated.

As illustrated in FIG. 3, a small tubing is lowered through casing 10 to adjacent perforations 14 and any sand or debris is washed from the well bore as the small tubing is run in. The plastic is then flowed through tubing 15 into perforations 14 and the formation 12. As is the usual practice, an afterflush is flowed down tubing 15 to wash excess plastic from the well bore.

Following this afterfiush, a second afterflush containing particles of sand, aluminum spheres, glass beads, small plastic cylinders, ground calcium carbonate, -or other particulate solids 16 that are not wet with the plastic are flowed down tubing 15 and placed in the perforation holes 14 as illustrated in FIG. 4. One quarter to three pounds of particulate solid material per gallon in a total of one to five barrels of afterfiush should be satisfactory for this step.

Following the solid-containing afterush solution, a prepared emulsion or filter cake building material is circulated down tubing 15 to form a filter cake cover 17 over the face of the perforation holes 14 containing the packed solids 16 as shown in FIG. 5. A continual, light pressure, P2 P1 is held on the well bore to exert a physical force which holds the filter material 17 against the packed perforation holes and prevents the backfiow of sand or particulate solids into the well bore due to gravity.

Tubing 15 is removed from the well bore and the plastic in the unconsolidated formation 12 is permitted to set and harden. v

As illustrated in FIG. 6, when the well is placed on production, the temporary packing material 16 and the filter cake 17 are carried from the perforation holes 14 as well as from small cavities behind casing 10. High productivity results from these conditions.

A practical procedure for sand control 'with plastic consolidation according to the invention is as follows:

(l) Following conventional perforation of the unconsolidated formation (with a pressure differential into the formation), a one-inch pipe is run into the perforated interval and the well bore is washed by circulation and reverse circulation to insure that all sand is washed out of the borehole. Reverse circulation is continued until clean water is obtained in the returns. The last water at the bottom of the hole just prior to discontinuing the wash operation should weigh 9.3 pounds/ gal. (p.p.g.) or more so that plastic will not tend to move downward past the perforations;

(2) Diesel oil is then circulated down the one-inch by 27s-inch annulus surrounding the one-inch pipe in sufficient volume to completely fill the annulus plus one-half barrel.

(3) After establishing that the perforation will accept clean fiuid at a reasonable pressure, 5 bbl. of preiiush (1% solution of Z-6020 in clean 9.0 -p.p..g. water) is bullheaded down the one-inch pipe (clean salt water is displaced into the perforations ahead =of the prefiush) followed by 3 bbl. of clean spacer water. Z-6020` is a trade name for a chemical agent manufactured and marketed by the Dow-Corning Corporation, Midland, Michigan. The compound is 2-aminoethyl aminopropyl trimethoxy silane. Silanes of this type promote bonding between the inorganic sand and the organic resin. A more complete -description of the use of the silane is described and claimed in U.S. patent application Ser. No. 183,751, entitled Sand Consolidation Method by Horace H. Spain, filed Mar. 30, 1962.

(4) The plastic ingredients are mixed according to the formation temperature anticipated and plastic is displaced behind the spacer fiuid.

(5) Introduction of the plastic mixture is followed by one to two bbl. of overflush (diesel oil containing 2% cresol). This first overflush is adjusted so that the formation is not overfiushed with more than 5 bbls. total.

(6) The first overiiush is followed by a packing overflush which is 2% cresol in diesel oil and containing 1A to 3% p.p.g. of ground calcium carbonate, (50450 mixture of 30-50 mesh and 40-200` mesh CaCO3). The packing overfiush is adjusted according to h-ow much sand has been produced. New wells are done with 2 bbl. total and 1A to 1/2 p.p.g. of CaCO3 added. Treatments after sanding up will have 4 bbls. total and 1/2 to 3A ppg. of CaCO3.

(7) The packing overflush is followed by Black Magic drilling mud to obtain a lock-up of pressure inside the tubing against the mud filter cake built up on the packed perforations. One drum (55 gal.) of Black Magic should be adequate for short perforated intervals of 10 holes or less; however, the amount of filter cake buil-ding material may be increased where necessary. Black Magic drilling mud is an oil base mud marketed by Oil Base, Inc. of Compton, Calif., which obtains filter cake building properties through emulsification and ground asphalt particles. Weight is obtained in the fiuid by adding ground calcium carbonate or barite.

(8) The drilling mud is displaced to the perforations until the injection pressure increases 400 p.s.i. as a result of CaCO3 packing or Black Magic filter cake building or both. After the 400 p.s.i. rise is obtained, pumping is resumed intermittently as pressure bleeds off until a pressure lock-up is obtained. At least Mt barrel of Black Magic is left in the well bore opposite the perforations regardless of pressure increase obtained.

A gelling agent may be added in the sixth step to insure that the solids are carried into the perforations.

Four wells treated according to this procedure were made to fiow after limited swabbing (about one-half day) whereas comparable completions have -previously required as much as three days swabbing to initiate fiow. Flowing tubing pressures were comparable to 200` p.s.i. higher than wells treated in the conventional manner. This tubing pressure was sometimes a increase in tubing pressure on the shallow (4000 to 5000) wells treated.

The invention described herein is not restricted to the specific mode of operation set forth as various modifications thereof may Ibe made without departing from the spirit and scope of the invention.

Having fully described the objects, advantages, and method of operation of my invention, I claim:

1. A method for consolidating the san-ds of an incompetent subsurface formation comprising the steps of:

perforating said formation to form a hole in said formation;

introducing a sand consolidating plastic into said perforation hole in said formation; introducing into said perforation hole in said formation behind said plastic solid particles not wetted with said plastic and adapted to be carried fr-om said perforation hole when said formation is produced; and

then producing said formation whereby the solid particles packed in said perforation hole are produced and high -productivity results through the void left by said solid particles.

2. A method as recited in claim 1 including maintaining a pressure differential on the well bore suicient to exert a physical force to hold said solid particles in said perforation hole.

3. A method as recited in claim 2 including the step of introducing into the well bore adjacent said perforation a filter cake building material capable of forming a filter cake cover over the face of said perforation packed with solid particles following the step of introducing said particles into said formation and prior to the step of maintaining a pressure differential on the well bore.

4. A method as recited in claim 3 including the step of flowing a portion of said formation fluids through said perforation into said well bore following the step of perforating said formation and prior to the step of introducing said sand consolidating plastic into said formation.

5. A method as recited in claim 4 in which a silane bonding agent adapted to promote bonding between the sand and plastic is introduced into said formation.

6. A method as recited in claim 5 in which said silane is introduced into said formation in a water solution prior to the step of introducing said sand consolidating plastic into said formation.

7. A method as `recited in claim 6 in which said solid particles are introduced into said formation in a mixture `of 2% cresol in diesel oil.

8. A method as recited in claim 7 in which said solid particles comprise calcium carbonate.

9. A method as recited in claim 8 in which said plastic is selected from the group consisting of phenol-formaldehyde type resin and epoxy type resin.

10. A method as recited in claim 9 in which said formation is perforated while maintaining a pressure differential into said Well bore.

11. A method as recited in claim 9 in which said formation is perforated while maintaining a pressure differential into said formation.

References Cited UNITED STATES PATENTS 2,986,538 5/1961 Nesbitt et al 166--33 X 3,022,825 2/ 1962 Winsaurer et al. 166--33 3,172,471 3/1965 Warren 166-33 3,280,912 10/1966 Sheflield 175-72 X CHARLES E. OCONNELL, Primary Examiner. DAVID H. BROWN, Examiner. 

1. A METHOD FOR CONSOLIDATING THE SANDS OF AN INCOMPETENT SUBSURFACE FORMATION COMPRISING THE STEPS OF: PERFORATING SAID FORMATION TO FORM A HOLE IN SAID FORMATION; INTRODUCING A SAND CONSOLIDATING PLASTIC INTO SAID PERFORATION HOLE IN SAID FORMATION; INTRODUCING INTO SAID PERFORATION HOLE IN SID FORMATION BEHIND SAID PLASTIC SOLID PARTICLES NOT WETTED WITH SAID PLASTIC AND ADAPTED TO BE CARRIED FROM SAID PERFORATION HOLE WHEN SAID FORMATION IS PRODUCED; AND THEN PRODUCING SAID FORMATION WHEREBY THE SOLID PARTICLES PACKED IN SAID PERFORMATION HOLE ARE PRODUCED AND HIGH PRODUCTIVITY RESULTS THROUGH THE VOID LEFT BY SAID SOLID PARTICLES. 